App From Apple Store Does Not Function

I downloaded the Sinclair Dinopay App on my Iphone 15. After entering/confirming my Email Address, and agreeing to Terms & Conditions, I pressed the NEXT button in upper right of screen. It did not react. I tried reinstalling the app, with same results. I tried the same process on my older ipad, and was able to complete all of the steps, creating an account. I then went back to my iphone and logged in to my account, but when I needed to press the LOGIN button (also on the upper right part of the screen) it was also non-responsive.

I would like to know what the problem is here? I reached out to Sinclair's customer service for help, and they are baffled as well. Is this a hardware problem on Apple?